SEOUL, Oct. 6 (Xinhua) -- South Korea saw its foreign exchange reserves jump to a 15-month high in September mainly due to a rise in the U.S. dollar-converted value of assets denominated in other currencies, the central bank said Tuesday.

According to the Bank of Korea (BOK), South Korea's foreign reserves amounted to 254.25 billion dollars, marking an on-month rise of 8.79 billion dollars.

The amount of foreign reserves, which stayed on a rise for the seventh straight month, hit the highest level since June 2008 when it marked 259.1 billion U.S. dollars, the BOK added.

The gain in September also marked the largest degree since May when foreign reserves rose by 14.29 billion U.S. dollars on month.

The rise in the foreign currency reserves comes amid the South Korean currency keeping up with its appreciating move, hitting a one-year high against the U.S. dollar on Monday.

Since March, the local currency has rose 34 percent against the U.S. dollar.

The BOK also attributed the gain to a weaker U.S. dollar, which boosted up the converted value of assets denominated in other currencies.

The BOK said it expects the foreign exchange reserves to rise above the previous record level around the end of this year given the U.S. dollar continues to be on the wane.

The upward trend in the reserves is likely to continue with the current account remaining in black and foreign currency liquidity previously distributed to banks being retrieved, the bank further explained.

As of the end of August, South Korea was the world's sixth-largest holder of foreign exchange reserves, following China, Japan, Russia, Taiwan and India.